1. Field Of The Invention
This invention relates to surgical implants and more particularly, to surgical procedures and appliances for intraarticular anterior and posterior ligament reconstruction.
2. Prior Art
It is well known by anyone who has participated in athletics that the human knee is injury prone, particularly from lateral forces applied thereto. W here the knee joint is considered by most laymen to be essentially a hinged joint, in reality it provides a complicated mechanical movement that would be nearly impossible to duplicate with present technology. ln operation, the human knee joint permits movement of flexion and extension in certain positions and even provides for a slight inward and outward rotation. Considering only movement of flexion and extension, the mechanical actions that take place in such movement include a certain amount of gliding and rotation along with the hinge action such that the same part of one articular surface of the distal fem ur or proximal tibia will not always be applied to the same part of the other articular surface, and the axis of motion is not fixed. In fact, if the knee joint is examined while in a condition of extreme flexion, the posterior part of the articular surfaces of the tibia will be found to be in contact with the femur posterior around the extremities of the condyles. Whereas, if the movement was simple hinge like movement, the axis around which the revolving movement of the tibia would occur should be in the back part of the condyle. With the same leg brought forward into a position of semi-flexion, the upper surface of the tibia will seem to glide over the condyle of the femur, such that the middlepart of the articular facets are in contact, and the axis of rotation is therefore shifted forward to near the center of the condyle. When the leg is brought into the extended position, still further gliding takes place as does a further shifting forward of the axis of rotation. Knee joint flexure and extension is therefore not a simple movement but is accompanied by a certain amount of outward rotation around a vertical axis drawn through the center of the head of the tibia. This rotation is due to the greater length of the internal condyle, and to the fact that the anterior portion of its articular surface is inclined obliquely outward. In consequence, towards the close of the movement of extension, just before complete extension, the tibia will glide obliquely upward and outward over the oblique surface of the inner condyle, and the leg will be necessarily rotated outwardly. In flexation of the joint, the converse of these movements takes place, the tibia gliding backwardly around the end of the femur, at the commencement of which movement, the tibia is directed downward and inward along the oblique curve of the inner condyle, thus causing an inward rotation to the leg.
The above sets out a brief summary of knee joint functioning that takes place in knee flexure and extension. It is provided to show that this functioning is far more than a hinge movement and involves inward and outward rotation. It should be apparent therefore that in a repair of one or more ligaments of the knee, particularly in an intraarticular anterior and posterior ligament reconstruction that involves the cruciate ligaments, it is of significant value that the replacement ligaments, either a graft or prosthetic ligament, be fitted so as to, as nearly as possible, duplicate the positioning of the natural ligament. Heretofore, procedures and devices for use in repairing damaged ligaments, particularly the cruciate ligaments, have generally involved attaching the ligament device across the knee at the juncture of the distal fem ur and proximal tibia surfaces. Where an attempt has been made to replace a cruciate ligament that involves securing the replacement ligament ends to the points on the opposing bone surfaces where that natural ligament was attached, such procedure has involved extensively opening the patient's knee area and/or forming intersecting tunnels through the respective tibia and femur ends and positioning a ligament therebetween. An example of such surgical technique and an implant device is shown in a patent by Hunt, et al., U.S. Pat. No. 4,590,928. This patent is directed to an implant and kit therefore but does not, as does the present invention, provide an arrangement that is a near duplication for the patient's natural ligament. Rather, the Hunt, et al. patent is devoted to connectors and an implant that incorporates carbon fibers and, where tunnels are shown formed in the respective bones, such are apparently formed where access is convenient. As the tunnels are not aligned and each is open to without the femur and tibia surfaces, their formation involves extensive opening of the knee to provide access to the bone surfaces. Unlike the Hunt, et. al. patent procedure, the present invention provides for ligament reconstruction using essentially an arthroscopic technique where a single incision only is made to the bone below the tibia tuberosity. From that point, a tunnel is formed into the bone that passes through the respective points of connection of a cruciate ligament between the proximal tibia and distal femur and into the femur cortex. The femur cortex is then prepared to receive a ligament end coupling fitted therein to secure one ligament end.
Earlier ligament replacement procedures have involved an extensive opening of the knee and have included forming passages or tunnels in the tibia and femur from the bone surfaces wherethrough are pulled a natural or artificial ligament, the ends of which ligament are bent and secured as with staples to the bone surfaces. Unlike such earlier procedures and arrangements, the present invention provides for both fitting a ligament to extend across the knee so as to most nearly duplicate the natural ligament positioning and provides for internal coupling the one ligament within a bone cortex. Additionally, the present invention provides a convenient arrangement for adjusting the implanted ligament tensioning to most nearly duplicate a natural condition. The present invention therefore provides both a unique surgical approach and attachment devices to produce and implant that most nearly duplicates the patient's natural ligament arrangement tham has heretofore been possible.